The expression of a high affinity mechanism of iron acquisition by Neisseria gonorrhoeae is presumed to be a prerequisite to infection. This notion has largely been inferred by in vitro studies on gonococcal iron-acquisition. Because of the lack of an adequate animal model, in vivo studies of this mechanism have been limited. This proposal focuses on the key role that the periplasm-to-cytosol transport of iron plays in the larger context of gonococcal iron-acquisition both in vitro and in vivo. Specifically we proposed to define the mechanism of gonococcal periplasm-to-cytosol iron transport both in Escherichia coli expressing the gonococcal system and within the gonococcus. Secondly, we propose to extend these studies to the level of gonococcal infection by analyzing whether the proteins (FbpA and the Tbps) involved in iron acquisition are expressed and functioning during symptomatic gonococcal cervicitis and asymptomatic disease. Finally we propose to comparatively evaluate the local immune response to FbpA and the Tbps in order to assess their immunogenecity during the course of gonococcal infection. These studies represent a comprehensive set of experiments spanning the process of gonococcal iron-acquisition from in vitro assays defining the molecular mechanism to the expression and immunogenecity of the systems in vivo. These experiments are made possible by the cooperation of several laboratories brought together by this program project grant. Specifically, our expertise in gonococcal iron-acquisition is complemented by the clinical core which will obtain the specimens analyzed in aims 2 and 3 of this proposal. The immunology core will perform expert analysis of the local immune response to FbpA and the Tbps. Collectively, these studies will significantly advanced our current understanding of the relationship between a high affinity gonococcal iron uptake system and disease.